// Copyright 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_
#define CC_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_

#include <memory>
#include <string>

#include "base/cancelable_callback.h"
#include "base/macros.h"
#include "base/memory/ptr_util.h"
#include "base/memory/weak_ptr.h"
#include "base/values.h"
#include "cc/base/cc_export.h"

namespace base {
namespace trace_event {
    class TracedValue;
}
class SingleThreadTaskRunner;
}

namespace cc {
class CC_EXPORT DelayBasedTimeSourceClient {
public:
    virtual void OnTimerTick() = 0;

protected:
    virtual ~DelayBasedTimeSourceClient() { }
};

// This timer implements a time source that achieves the specified interval
// in face of millisecond-precision delayed callbacks and random queueing
// delays. DelayBasedTimeSource uses base::TimeTicks::Now as its timebase.
class CC_EXPORT DelayBasedTimeSource {
public:
    explicit DelayBasedTimeSource(base::SingleThreadTaskRunner* task_runner);
    virtual ~DelayBasedTimeSource();

    void SetClient(DelayBasedTimeSourceClient* client);

    void SetTimebaseAndInterval(base::TimeTicks timebase,
        base::TimeDelta interval);

    base::TimeDelta Interval() const;

    void SetActive(bool active);
    bool Active() const;

    // Get the last and next tick times. NextTickTime() returns null when
    // inactive.
    base::TimeTicks LastTickTime() const;
    base::TimeTicks NextTickTime() const;

    virtual void AsValueInto(base::trace_event::TracedValue* dict) const;

protected:
    // Virtual for testing.
    virtual base::TimeTicks Now() const;
    virtual std::string TypeString() const;

private:
    void PostNextTickTask(base::TimeTicks now);
    void ResetTickTask(base::TimeTicks now);

    void OnTimerTick();

    DelayBasedTimeSourceClient* client_;

    bool active_;

    base::TimeTicks timebase_;
    base::TimeDelta interval_;

    base::TimeTicks last_tick_time_;
    base::TimeTicks next_tick_time_;

    base::CancelableClosure tick_closure_;

    base::SingleThreadTaskRunner* task_runner_;

    base::WeakPtrFactory<DelayBasedTimeSource> weak_factory_;

    DISALLOW_COPY_AND_ASSIGN(DelayBasedTimeSource);
};

} // namespace cc

#endif // CC_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_
